[PATCHv3 3/3] dynamic_debug: Add a flag for dynamic event tracing

[Sai Prakash Ranjan]

Debugging a specific driver or subsystem can be a lot easier if we can
trace events specific to that driver or subsystem. This type of
filtering can be achieved using existing dynamic debug library which
provides a way to filter based on files, functions and modules.

Using this, provide an additional flag 'e' to filter event tracing to
specified input.

For example, tracing all MMIO read/write can be overwhelming and of no
use when debugging a specific driver or a subsystem. So switch to
dynamic event tracing for register accesses.

Example: Tracing register accesses for all drivers in drivers/soc/qcom/*
and the trace output is given below:

  # dyndbg="file drivers/soc/qcom/* +e" trace_event=rwmmio
    or
  # echo "file drivers/soc/qcom/* +e" > /sys/kernel/debug/dynamic_debug/control
  # cat /sys/kernel/debug/tracing/trace
    rwmmio_read: rpmh_rsc_probe+0x35c/0x410 readl addr=0xffff80001071000c
    rwmmio_read: rpmh_rsc_probe+0x3d0/0x410 readl addr=0xffff800010710004
    rwmmio_write: rpmh_rsc_probe+0x3b0/0x410 writel addr=0xffff800010710d00 val=0x3
    rwmmio_write: write_tcs_cmd+0x6c/0x78 writel addr=0xffff800010710d30 val=0x10108

Cc: Jason Baron <jbaron at akamai.com>
Signed-off-by: Sai Prakash Ranjan <quic_saipraka at quicinc.com>
---
 include/linux/dynamic_debug.h     |  1 +
 include/linux/mmio-instrumented.h | 29 +++++++++++++++++++++++++++--
 lib/dynamic_debug.c               |  1 +
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index dce631e678dd..80a1ae234a3b 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -32,6 +32,7 @@ struct _ddebug {
 #define _DPRINTK_FLAGS_INCL_FUNCNAME	(1<<2)
 #define _DPRINTK_FLAGS_INCL_LINENO	(1<<3)
 #define _DPRINTK_FLAGS_INCL_TID		(1<<4)
+#define _DPRINTK_FLAGS_EVENT		(1<<5)
 
 #define _DPRINTK_FLAGS_INCL_ANY		\
 	(_DPRINTK_FLAGS_INCL_MODNAME | _DPRINTK_FLAGS_INCL_FUNCNAME |\
diff --git a/include/linux/mmio-instrumented.h b/include/linux/mmio-instrumented.h
index 4304224f3be4..4ff5af4bbee8 100644
--- a/include/linux/mmio-instrumented.h
+++ b/include/linux/mmio-instrumented.h
@@ -6,6 +6,7 @@
 #ifndef _LINUX_MMIO_INSTRUMENTED_H
 #define _LINUX_MMIO_INSTRUMENTED_H
 
+#include <linux/dynamic_debug.h>
 #include <linux/tracepoint-defs.h>
 
 /*
@@ -25,7 +26,7 @@ void log_read_mmio(const char *width, const volatile void __iomem *addr);
 #define __raw_write(v, a, _l)	({				\
 	volatile void __iomem *_a = (a);			\
 	if (tracepoint_enabled(rwmmio_write))			\
-		log_write_mmio(__stringify(write##_l), v, _a);	\
+		dynamic_log_write_mmio(__stringify(write##_l), v, _a);\
 	arch_raw_write##_l((v), _a);				\
 	})
 
@@ -38,7 +39,7 @@ void log_read_mmio(const char *width, const volatile void __iomem *addr);
 	_t __a;							\
 	const volatile void __iomem *_a = (a);			\
 	if (tracepoint_enabled(rwmmio_read))			\
-		log_read_mmio(__stringify(read##_l), _a);	\
+		dynamic_log_read_mmio(__stringify(read##_l), _a);\
 	__a = arch_raw_read##_l(_a);				\
 	__a;							\
 	})
@@ -48,6 +49,26 @@ void log_read_mmio(const char *width, const volatile void __iomem *addr);
 #define __raw_readl(a)		__raw_read((a), l, u32)
 #define __raw_readq(a)		__raw_read((a), q, u64)
 
+#if defined(CONFIG_DYNAMIC_DEBUG)
+#define dynamic_log_write_mmio(width, value, addr)		\
+do {								\
+	DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, width);	\
+	if (unlikely(descriptor.flags & _DPRINTK_FLAGS_EVENT))	\
+		log_write_mmio(width, value, addr);		\
+} while (0)
+
+#define dynamic_log_read_mmio(width, addr)			\
+do {								\
+	DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, width);	\
+	if (unlikely(descriptor.flags & _DPRINTK_FLAGS_EVENT))	\
+		log_read_mmio(width, addr);			\
+} while (0)
+
+#else
+#define dynamic_log_write_mmio(width, val, addr)	log_write_mmio(width, val, addr)
+#define dynamic_log_read_mmio(width, addr)		log_read_mmio(width, addr)
+#endif /* CONFIG_DYNAMIC_DEBUG */
+
 #else
 
 #define __raw_writeb(v, a)	arch_raw_writeb(v, a)
@@ -64,6 +85,10 @@ static inline void log_write_mmio(const char *width, u64 val,
 				  volatile void __iomem *addr) {}
 static inline void log_read_mmio(const char *width,
 				 const volatile void __iomem *addr) {}
+static inline void dynamic_log_write_mmio(const char *width, u64 val,
+				  volatile void __iomem *addr) {}
+static inline void dynamic_log_read_mmio(const char *width,
+				 const volatile void __iomem *addr) {}
 
 #endif /* CONFIG_TRACE_MMIO_ACCESS */
 
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index dd7f56af9aed..a852073089d9 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -87,6 +87,7 @@ static inline const char *trim_prefix(const char *path)
 
 static struct { unsigned flag:8; char opt_char; } opt_array[] = {
 	{ _DPRINTK_FLAGS_PRINT, 'p' },
+	{ _DPRINTK_FLAGS_EVENT, 'e' },
 	{ _DPRINTK_FLAGS_INCL_MODNAME, 'm' },
 	{ _DPRINTK_FLAGS_INCL_FUNCNAME, 'f' },
 	{ _DPRINTK_FLAGS_INCL_LINENO, 'l' },
-- 
2.29.0